Basic Principles


  1. Water constitutes over 50% of individual's weight; largest single component.
  2. Body water divided into two compartments
    1. Intracellular: within cells
    2. Extracellular: outside cells, further divided into interstitial and intravascular fluid
  3. Fluids in two compartments move among cells, tissue spaces, and plasma


  1. Salts or minerals in extracellular or intracellular body fluids
  2. If positively charged, called cations; if negatively charged, called anions
  3. Common electrolytes and normal blood values
    1. Sodium (Na)--135-148 mEq/liter
    2. Potassium (K)--3.5-5 mEq/liter
    3. Calcium (Ca)--4.5-5.3 mEq/liter, 9-11 mg/dl
    4. Magnesium (Mg)--1.3-2.1 mEq/liter
    5. Chloride (Cl)--98-106 mEq/liter

Movement of Fluids and Electrolytes

  1. Diffusion: movement of particles from an area of greater concentration to an area of lesser concentration as part of random activity
  2. Active transport: movement across cell membranes requiring energy from an outside source
  3. Osmosis: movement of water through a semipermeable membrane

Fluid and Electrolyte Imbalances
See Table 4.5.

  1. Hypovolemia: extracellular fluid volume deficit
  2. Hypervolemia: extracellular fluid volume excess
  3. Water excess: hypo-osmolar imbalances; water intoxication or solute deficit
  4. Water deficit: hyperosmolar imbalances; water depletion or solute excess
  5. Hyperkalemia: potassium excess, serum potassium above 5.5 mEq/liter
  6. Hypokalemia: potassium deficit, serum potassium below 3 mEq/liter
  7. Hypernatremia: sodium excess, serum sodium level above 145 mEq/liter
  8. Hyponatremia: sodium deficit, serum sodium level below 135 mEq/liter
  9. Hypercalcemia: calcium excess, serum calcium level above 5.8 mEq/liter
  10. Hypocalcemia: calcium deficit, serum calcium level below 4.5 mEq/liter
  11. Hypermagnesemia: magnesium excess, serum magnesium level above 3 mEq/liter
  12. Hypomagnesemia: magnesium deficit, serum magnesium level below 1.5 mEq/liter

Table 4.5 Fluid and Electrolyte Imbalances



Assessment Findings

Nursing Interventions

Hypovolemia (extracellular fluid volume deficit)

Hemorrhage, diarrhea, vomiting, kidney disease, diaphoresis, burns, fever, draining fistulas, sequestration of fluids (peritonitis, edema associated with burns)

Nausea and vomiting, weakness, weight loss, anorexia, longitudinal wrinkles of the tongue, dry skin and mucous membranes, decreased fullness of neck veins, postural hypotension, oliguria to anuria, shock

Measure I&O.
Weigh daily.
Monitor closely and regulate isotonic IV infusion.
Monitor blood pressure (determine lying down, sitting, and standing).
Report urine output less than 30 ml/hr.
Carefully assess skin and mucous membranes.
Monitor for signs of shock.

Hypervolemia (extracellular fluid volume excess)

Excess or too rapid administration of any isotonic solution; side effect of corticosteroid administration; cardiac, liver, or renal disease; cerebral damage; stress

Weight gain, pitting edema, dyspnea, cough, diaphoresis, frothy or pink-tinged sputum, edema of the eyelids, distended neck veins, elevated blood pressure, moist rales (crackles)

Weigh daily.
Measure I&O.
Regulate IV fluids/administration of diuretics strictly and monitor carefully.
Monitor abdominal girth.
Assess for pitting edema.
Restrict sodium and water intake.

Water excess syndromes

Excessive intake of water, inability to excrete water due to kidney or brain damage, excessive administration of electrolyte-free solutions, poor salt intake, use of diuretics, irrigation of nasogastric tube with plain water, administration of excessive amount of ice chips to a vomiting client or one with a nasogastric tube

Polyuria (in absence of renal disease), oliguria (with renal disease), twitching, hyperirritability, disorientation, coma, convulsions, abdominal cramps

Measure I&O.
Weigh daily.
Restrict oral and IV intake.
Replace fluid losses with isotonic solutions.
Use normal saline solution for nasogastric tube irrigation.

Water deficit syndromes

Increased water output due to watery diarrhea, diabetic acidosis, excess TPN; dysphagia; impaired thirst mechanism; coma; general debility; diaphoresis; excess protein intake without sufficient water intake

Thirst, poor skin turgor, dry skin and mucous membranes, dry furrowed tongue, sunken eyeballs, weight loss, elevated temperature, apprehension, oliguria to anuria

Measure I&O.
Weigh daily.
Assess skin frequently.
Ensure that clients with a high solute intake receive adequate water.
Assess vital signs frequently, particularly temperature.
Monitor TPN infusions accurately.


Renal insufficiency, adrenocortical insufficiency, cellulose damage (burns), infection, acidotic states, rapid infusion of IV solutions with potassium, overzealous administration of potassium-conserving diuretics

Thready, slow pulse; shallow breathing; nausea and vomiting; diarrhea; intestinal colic, irritability; muscle weakness, numbness, flaccid paralysis; tingling; difficulty with phonation, respiration

Administer Kayexalate as ordered.
Administer/monitor IV infusion of glucose and insulin.
Control infection.
Provide adequate calories and carbohydrates.
Discontinue IV or oral sources of potassium.


Anorexia, alcoholism, gastric and intestinal suction, GI surgery, vomiting, diarrhea, laxative abuse, thiazide diuretics, steroid therapy, stress, alkalotic states

Thready, rapid, weak pulse; faint heart sounds; decreased blood pressure; skeletal muscle weakness; decreased or absent reflexes; shallow respirations; malaise; apathy; lethargy; loss of orientation; anorexia, vomiting, weight loss, gaseous intestinal distention

Be especially cautious if administering drugs that are not potassium sparing.
Administer potassium supplements to replace losses.
Monitor acid-base balance.
Monitor pulse, blood pressure, and ECG.


Excessive/rapid IV administration of normal saline solution, inadequate water intake, kidney disease

Dry, sticky mucous membranes; flushed skin; rough, dry tongue; firm skin turgor; intense thirst; edema; oliguria to anuria

Weigh daily.
Assess degree of edema frequently.
Measure I&O.
Assess skin frequently and institute nursing measures to prevent breakdown.
Encourage sodium-restricted diet.


Decreased sodium intake, increased sodium excretion through diaphoresis or GI suctioning, adrenal insufficiency

Nausea and vomiting; abdominal cramps; weight loss; cold, clammy skin; decreased skin turgor; fingerprinting over the sternum; shrunken tongue; apprehension; headache; convulsions; confusion; weakness; fatigue; postural hypotension; rapid, thready pulse

Provide foods high in sodium.
Administer normal saline solution IV.
Assess blood pressure frequently (measure lying down, sitting, and standing)


Hyperparathyroidism, immobility, increased vitamin D intake, osteoporosis and osteomalacia (early stages)

Nausea and vomiting, anorexia, constipation, headache, confusion, lethargy, stupor, decreased muscle tone, deep bone and/or flank pain

Encourage mobilization.
Limit vitamin D and calcium intake.
Administer diuretics.
Protect from injury


Acute pancreatitis, diarrhea, hypoparathyroidism, lack of vitamin D in diet, long-term steroid therapy

Painful tonic muscle spasms, facial spasms, fatigue, laryngospasm, positive Trousseau's and Chvostek's signs, convulsions, dyspnea

Administer oral calcium lactate or IV calcium chloride or gluconate.
Provide safety by padding side rails.
Administer dietary sources of calcium.
Provide quiet environment.


Renal insufficiency, dehydration, excessive use of magnesium-containing antacids or laxatives

Lethargy, somnolence, confusion, nausea and vomiting, muscle weakness, depressed reflexes, decreased pulse and respirations

Withhold magnesium-containing drugs/foods.
Increase fluid intake (unless contraindicated)


Low intake of magnesium in diet, prolonged diarrhea, massive diuresis, hypoparathyroidism

Paresthesias, confusion, hallucinations, convulsions, ataxia, tremors, hyperactive deep reflexes, muscle spasm, flushing of the face, diaphoresis

Provide good dietary sources of magnesium


Basic Principles

  1. Normal pH of the body is 7.35-7.45.
  2. Buffer or control systems maintain normal pH. Kidneys excrete acids and reabsorb bicarbonate while the respiratory system gives off carbon dioxide in acidic states. In alkalotic states, the kidneys excrete bicarbonate and the respiratory system retains carbonic acid.

Acid-Base Imbalances
See Table 4.6.

  1. Metabolic acidosis: a primary deficit in the concentration of base bicarbonate in the extracellular fluid; decreased pH and bicarbonate, decreased pCO2 (if lung compensation)
  2. Metabolic alkalosis: a primary excess of base bicarbonate in the extracellular fluid; elevated pH and bicarbonate, elevated pCO2 (if lung compensation)
  3. Respiratory acidosis: a primary excess of carbonic acid in the extracellular fluid; decreased pH, elevated pCO2 and bicarbonate (if renal compensation)
  4. Respiratory alkalosis: a primary deficit of carbonic acid in the extracellular fluid; elevated pH, decreased pCO2 and bicarbonate (if renal compensation)

Table 4.6 Acid - Base Imbalances



Assessment Findings

Nursing Interventions

Metabolic acidosis

Diabetic ketoacidosis, uremia, starvation, diarrhea, severe infections, renal tubular acidosis

Headache, nausea and vomiting, weakness, lethargy, disorientation, tremors, convulsions, coma

Administer sodium bicarbonate as ordered and monitor for signs of excess.
Monitor for signs of hyperkalemia.
Provide alkaline mouthwash (baking soda and water) to neutralize acids.
Lubricate lips to prevent dryness from hyperventilation.
Measure I&O.
Institute seizure precautions.
Monitor arterial blood gases and electrolytes.

Metabolic alkalosis

Severe vomiting, nasogastric suctioning, diuretic therapy, excessive ingestion of sodium bicarbonate, biliary drainage

Nausea and vomiting, diarrhea, numbness and tingling of extremities, tetany, bradycardia, decreased respirations

Replace fluid and electrolyte losses (potassium and chloride).
Institute seizure precautions.
Measure I&O.
Assess for signs of hypokalemia.
Monitor arterial blood gases and electrolytes.

Respiratory acidosis

COPD, barbiturate or sedative overdose, acute airway obstruction, weakness of respiratory muscles

Headache, weakness, visual disturbances, rapid respirations, confusion, drowsiness, tachycardia, coma

Position in semi-Fowler's.
Maintain patent airway.
Turn, cough, and deep breathe.
Perform postural drainage.
Administer fluids to help liquefy secretions (unless contraindicated).
Administer low-concentration oxygen therapy.
Monitor arterial blood gases and electrolytes.
Administer prophylactic antibiotics as ordered.

Respiratory alkalosis

Hyperventilation, mechanical overventilation, encephalitis

Numbness and tingling of mouth and extremities, inability to concentrate, rapid respirations, dry mouth, coma

Offer reassurance.
Encourage breathing into a paper bag or voluntary breath holding.
Ensure adequate rest.
Provide sedation as ordered.
Monitor mechanical ventilation, arterial blood gases, and electrolytes.